A seismic telemetry system employing a transmission line for data handling from remote units is disclosed in pending application Ser. No. 412,763, filed Nov. 5, 1973, by Wesley L. Joosten, et al, now abandoned and the application of Wesley L. Joosten, et al, Ser. No. 699,714 defined June 25, 1976, a continuation of the first-referenced application, itself now abandoned and the application of Wesley L. Joosten, Ser. No. 751,061 filed Dec. 6, 1976, a continuation of the second-referenced application.
The last-referenced application is assigned to the assignee of the present application. The disclosure of that application is hereby incorporated by reference, and for convenience the system therein disclosed will be referred to as the TDM (time division multiplex) cable system. As will be shown hereafter, the present invention permits a significant increase in date rate of the system. In the seismic business today, there is an ever-increasing demand for larger data rates. These larger rates are mandated by one or more of the following: Shorter sampling intervals; more accurate measurement of seismic signals (more bits per sampling); and more data acquisition points per shot. The present invention accomplishes those objectives, as will appear from the description to follow.